Liquid-liquid extraction of cadmium(II) from sulfate medium using phosphonium and ammonium based ionic liquids diluted in kerosene

The experimental results of cadmium extraction from sulfate medium using two ionic liquids trihexyl (tetradecyl)phosphonium chloride (Cyphos IL 101) and trioctylmethylammonium chloride (Aliquat 336) diluted in kerosene were presented. The extraction of cadmium was more pronounced with Cyphos IL 101 in comparison to Aliquat 336. The percentage extraction of cadmium increased with increase in aqueous phase pH with Aliquat 336 whilst it does not vary so much with Cyphos IL 101. Fast extraction equilibrations were achieved for both Cyphos IL 101 and Aliquat 336. Quantitative extraction (99%) of cadmium ions was found using 0.04 M Cyphos IL101 and 0.2 M Aliquat 336, respectively. The extraction processes were endothermic for both ionic liquids. The proposed complexes formed in the organic phases were CdSO4·3R3R′PCl for Cyphos IL 101 and CdSO4·3R3R′NCl for Aliquat 336. Different stripping agents were tested for complete back extraction of cadmium from the loaded organic phases and 70% of cadmium ions were stripped using 0.1 M EDTA + ammonia buffer in 1:1 ratio from the loaded organic phase of Cyphos IL 101 whereas 0.1 M EDTA + ammonia buffer in 4:1 ratio could strip 75% cadmium form the loaded organic phase of Aliquat 336. Separation of cadmium from nickel and zinc was possible from a ternary mixture containing 0.1 gpL of each metal ion using 0.04 M Cyphos IL 101 in kerosene. Mc-Cabe-Thiele plot showed that cadmium could be completely removed from the mixture in two stages at O:A ratio of 2:3.